I've completed the whole process. There were 5 stages:

• Initial screening call. Pretty standard stuff.
• Coding interview. Live-coding task with one of the senior devs from Samsara. That happened a week after the first stage.

After that, I was invited to the last 3 stages, which happened in a single day:

• System Design. Very nice, as it was different from the usual "Design a Twitter/Youtube/Spotify" prompt, but was a lot closer to actual day-to-day work.
• Interview with the Hiring Manager. Very nice call, mostly about previous work experience, how to handle specific situations, etc.
• Coding interview II. Again, live coding.

I signed an NDA, so no details here.